A display device incorporating a display panel configured to display an image and a touch panel adapted for touch sensing to detect user input provides a convenient user interface.
Capacitive sensing is one of touch sensing technologies. Some capacitive sensing technologies may be based on self-capacitance (also referred to as “absolute capacitance”) sensing and/or mutual capacitance (also referred to as “transcapacitance”) sensing. The self-capacitance sensing involves obtaining a sensing signal dependent on the self-capacitance of a sense electrode provided in the touch panel while the mutual capacitance sensing involves obtaining a sensing signal dependent on the mutual capacitance between a sense electrode and a drive electrode. Capacitive touch sensing is disclosed in Japanese Patent Application Publication No. 2015-141556.
A display panel may incorporate electrodes used for touch sensing, which may include sense electrodes and/or drive electrodes. For example, a liquid crystal display panel of this type may include common electrodes arrayed in rows and columns, and the common electrodes may also be used as sense electrodes or drive electrodes in touch sensing. Use of this type of display panel effectively reduces the volume of the entire display device, and may be suitable for application to mobile terminals.
Touch sensing may be performed in a blanking period during which image displaying is stopped. For example, after completion of a display period during which respective pixel circuits are driven in response to display data, the source lines are set to a predetermined potential, most typically, to the circuit ground level, to stabilize the electric state of the display panel, and then touch sensing is performed on the basis of sensing signals obtained from the sense electrodes.
Such touch sensing may suffer from noise applied to the sense electrodes. The operation to drive the source lines to the predetermined potential after the completion of the display period may cause changes in the potentials of conductors provided near the source lines, such as gate lines, in the active area. The changes in the potentials of the conductors may generate noise applied to the sense electrodes. Touch sensing may be performed after the noise is sufficiently attenuated to achieve precise touch sensing.